Aneurysms have conventionally been treated surgically with varying degrees of success. However, surgical treatment of vascular aneurysms continues to involve a high degree of risk to the patient and can result in surgical mortality and disability.
One method for treating aneurysms that is less traumatic and which reduces or eliminates the need for surgical intervention involved the use of a fixed balloon catheter to artificially embolize the vessel leading to the aneurysms. The non-detachable balloon evolved into a detachable balloon delivered on an intra-arterial flexible catheter and was used clinically as early as 1972. Subsequent clinical work has also used detachable balloons with gradually improving results.
Detachable balloons generally employ three main features: a shell or membrane for containing an inflation medium, a sealing mechanism to close the shell or membrane after detachment of the balloon, and an attachment which maintains a connection to a delivery device until detachment of the balloon is desired. In the past, balloon membranes were fabricated from highly resilient elastic materials such as natural latex which provided an adequate container; however, an inflated balloon formed of latex becomes very hard and does not readily conform to surrounding tissue. Also, some aneurysms have varying shapes for which a spherical balloon may not appropriately fill.
The most commonly used sealing mechanisms employed in the past consisted of a simple elastic “string” tied around the neck of the balloon by each user; however, this has been proved to be unreliable. Improved sealing mechanisms have been used but their complexity or size has prevented them from being used successfully in some vessels, such as cerebral blood vessels which are usually fragile.
Detachable balloons are generally inflated with a suitable fluid, typically a polymerizable resin, and released from the end of the catheter. However, when using intravascular balloon embolization of intracranial berry aneurysms, inflation of a balloon into the aneurysm carries some risk of aneurysm rupture due to possible “overfilling” of portions of the sac and due to the traction produced when detaching the balloon from the end of the catheter.
Moreover, a vascular balloon is difficult to retrieve after the resin within the balloon sets up, and the balloon cannot be easily visualized using radiographic techniques unless it is filled with contrast material. Balloons have also been known to rupture during filling, or release prematurely during filling, or leak monomeric resin into the vasculature during the period before the monomer sets up into polymeric form.
A balloon delivery catheter used for artificial vessel embolization is described in U.S. Pat. No. 4,819,637 to Dormandy, Jr. et al., which is incorporated herein by reference in its entirety. Dormandy describes a detachable balloon delivery catheter which includes a cylindrical valve base and a self-sealing valve mounted on the valve base. However, Dormandy does not show or describe a balloon which can self-expand while aspirating blood within the balloon to form an embolic occlusion within an aneurysm.
U.S. Pat. No. 5,456,666 to Campbell et al., which is incorporated herein by reference in its entirety, describes a medical balloon which can fold into predetermined shapes and is expandable from a folded condition for insertion into the body. However, Campbell likewise does not show or describe a self-expanding balloon which can aspirate blood.
U.S. Pat. No. 5,458,572 to Campbell et al., which is also incorporated herein by reference in its entirety, also describes a balloon which is adapted to be folded into predetermined configurations. The balloon is adapted for inflation from a folded configuration to an inflated, expanded configuration and back to the folded configuration. However, Campbell also does not show or describe a self-expanding balloon which can aspirate blood.
Therefore, there is a need for a balloon device which can adequately conform to the surrounding interior tissue of an aneurysm and also eliminate the dangers of aneurysm rupture due to overfilling of the balloon.